Fatigue failure of high precision spindle bearing under extreme service conditions

Four sets of high precision spindle bearings (HPSB) had been in extreme service for 6040 h and 85,000 r/min. The service temperature, wear fatigue form, hardness, residual stress, retained austenite, metamorphic layer and element content of the bearing raceway were analyzed. The surface layer and inner layer of bearing raceway were analyzed by Electron Backscatter Diffraction (EBSD), Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM). The results show that the service temperature range of the four sets of bearings is from 17.5 degrees C to 74.7 degrees C. With the increase of rotating speed, the bearing temperature can reach 65 degrees C at 85,000 r/ min. The four sets of bearings have different degrees of wear, including fatigue shedding (FS), wear (W), corrosion (C), peristalsis (P), burn (B) and defect (D). In the extreme speed service, taking the bearing No.2 with the highest temperature as the research object, the maximum and minimum hardness differences of outer ring raceway, inner ring raceway and ball are 423.1 HV, 368.7 HV and 405 HV, respectively. The tangential residual stresses of the outer and inner ring raceways are found to be tensile stresses, which are 31.3 MPa and 110.8 MPa, respectively. The retained austenite in the outer and inner ring raceways of bearings are found to increase abnormally, reaching 36.7 % and 34.7 %, respectively. In addition to the highest Ion (Fe) element, the outer and inner ring raceways of bearings also contain higher Praseodymium (Pr) elements, reaching 35.5 % and 14.5 %, respectively. The maximum thickness of the "white layer" of the outer and inner ring raceways of the bearing is 15 mu m and 17 mu m, respectively. The surface layer of bearing outer and inner ring raceways contain nanocrystals of 200 nm and 100 nm, respectively. Certain nanocrystalline layer will prolong the service life of bearings. Nanocrystals mainly contain Phosphorus (P) and Copper (Cu) elements. The research findings of this study can provide theoretical and data support for enterprises and scholars in the engineering field.